It seems that 

https://code.google.com/p/go/source/detail?r=a90503e16fd4fc1d4449bc5e1fbcb8d33227d466
runtime: convert a few traceback-related functions from proc.c to traceback.go

... broken arm5:

http://build.golang.org/log/66e37b389c69e213eda50d3e4d3b4f9defe32647
cmd/go
unexpected fault address 0x0
fatal error: fault
[signal 0x7 code=0x1 addr=0x0 pc=0x756f4]

goroutine 1 [running, locked to thread]:
runtime.throw(0x3320be)
    /usr/local/go/src/pkg/runtime/panic.c:515 +0x60 fp=0x1051bf50 sp=0x1051bf44
runtime.sigpanic()
    /usr/local/go/src/pkg/runtime/os_linux.c:233 +0x1bc fp=0x1051bf5c sp=0x1051bf50
runtime.funcPC(0x1d58e8, 0x339c82, 0x1d58e8)
    /usr/local/go/src/pkg/runtime/proc.go:117 +0x18 fp=0x1051bf60 sp=0x1051bf60
runtime.init()
    /usr/local/go/src/pkg/runtime/traceback.go:596 +0x354 fp=0x1051bf8c sp=0x1051bf60
runtime.main()
    /usr/local/go/src/pkg/runtime/proc.c:246 +0x94 fp=0x1051bfc4 sp=0x1051bf8c
runtime.goexit()
    /usr/local/go/src/pkg/runtime/proc.c:1519 fp=0x1051bfc4 sp=0x1051bfc4


and

https://code.google.com/p/go/source/detail?r=1bc626afe666112f7a74cebe058191acebd06023
cmd/cgo, runtime: write cgo stub wrappers in Go, not C

broken the rest of the ARM builders:

http://build.golang.org/log/1b87706a448ac17b3e0ae30cd8c3571fff288de4
testing/iotest
testing/quick
text/scanner

unexpected fault address 0x1071df7c
fatal error: fault
[signal 0xb code=0x2 addr=0x1071df7c pc=0x1071df7c]

goroutine 1 [running]:
runtime.throw(0x5276d2)
    /usr/local/go/src/pkg/runtime/panic.c:517 +0x60 fp=0xbeebbcd8 sp=0xbeebbccc
runtime.sigpanic()
    /usr/local/go/src/pkg/runtime/os_linux.c:241 +0xfc fp=0xbeebbce4 sp=0xbeebbcd8
# Testing packages.
unexpected fault address 0x1071df7c
fatal error: fault
[signal 0xb code=0x2 addr=0x1071df7c pc=0x1071df7c]

goroutine 1 [running]:
runtime.throw(0x5276d2)
    /usr/local/go/src/pkg/runtime/panic.c:517 +0x60 fp=0xbe916cc8 sp=0xbe916cbc
runtime.sigpanic()
    /usr/local/go/src/pkg/runtime/os_linux.c:241 +0xfc fp=0xbe916cd4 sp=0xbe916cc8